Forming non-woven fibrous material

ABSTRACT

Water-repellent non-woven fibrous sheet material is formed from a suspension of fibres in a foam containing a liquid medium, a gas, and a surface active agent. The sheet material formed from the suspension is treated to destroy the surface active agent via chemical reaction with polyvalent metal cations and is then saturated with an organic water-repellent material and is heated to effect drying of the sheet material.

Unite States Patent I191 Clarke et a1. Oct. 1, 1974 [54] FORMING NON-WOVEN FIBROUS 3,062,679 11/1962 Herdle et al. 162/135 MATERAL 3,542,640 11 1970 Friedberg et al. 162/101 3,716,449 2/1973 Gatward et a1. 162/183 [75] Inventors: David George Clarke, Langley,

g g a fi g gg Widmer FOREIGN PATENTS OR APPLICATIONS 11 near 1g ycom e; Martin Graham Smith, Amersham, all of 2,013,850 10/1970 France 162/168 England Primary Examiner-S. Leon Bashore [73] AssIgnee: Wiggins Teape Re search & Assistant Examiner peter Chin Development London Attorney, Agent, or Firm-Burns, Doane, Swecker 8L England Mathis [22] Filed: Sept. 12, 1972 [21] Appl. No.: 288,424 [57] ABSTRACT [30] Foreign Application Priority Data Water-repellent non-woven fibrous sheet material is S formed from a suspenslon of fibres In a foam containept. 20, Great Bl'ltalll a medium, a ga and a su f e a i e agent The sheet material formed from the suspension is l62/l0:),2l16d21(8)5) treated to destroy the Surface active agent via Chemi 58] d 185 4 cal reaction with polyvalent metal cations and is then le 0 earc l 6 saturated with an organic water-repellent material and l is heated to effect drying of the sheet material.

[56] References Cited 12 Claims, N0 Drawings FORMING NON-WOVEN FIBROUS MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to non-woven fibrous sheet material, for example paper, and particularly to a method of producing a water-repellent non-woven fibrous sheet material.

2. Description of the Prior Art.

A known method of producing a water-repellent fibrous sheet material is to laminate a polyethylene film to one surface of the sheet material.

However, whilst this provides virtually perfect water repellency properties for the sheet material, the resultant sheet material is of zero porosity, and for many applications a porous non-woven fibrous sheet material is required.

Another method of producing a water-repellent fibrous sheet material has theretofore been used, in which method the sheet material is treated, for example by saturation, with a water-repellent material, for example silicone, zirconium wax, or aluminium wax, in order to render the individual fibers of the sheet material strongly hydrophobic while leaving the structure of the sheet material, and thus the porosity thereof, virtually unaffected.

Recently it has been proposed to produce non-woven fibrous sheet material from a suspension of fibres in a foam containing a liquid medium (e.g., water), a gas (e.g., air) and a surface active agent (see for example British Pat. specification No. 1 129 757).

Such production of non-woven fibrous sheet material offers many advantages over other wet-laying and drylaying methods of production, but also presents the difficulty that the sheet material produced normally contains an amount of surface active agent sufficient adversely to affect the water repellency properties of the sheet material. This is because the surface active agent, being a wetting agent, is virtually the exact opposite of a water repellent.

Attempts to produce a water-repellent non-woven fibrous sheet material from sheet material produced by a foam method described above, by treating the sheet material with a water-repellent material as described above, have been only partially successful. In particular, it has not been possible with this method to produce a sheet material resistant to a 100 mm head of water for 30 minutes.

SUMMARY According to this invention a method of producing a water-repellent non-woven fibrous sheet material, comprises the steps of forming a suspension of fibres in a foam containing a liquid medium, a gas, and a surface active agent; forming a non-woven fibrous sheet mate;

DESCRIPTION OF PREFERRED EMBODIMENTS In carrying the invention into effect a suspension of fibres in a foam containing a liquid medium, usually water; a gas, usually air; and a surface active agent is agent can be destroyed by treatment with a 2 to 5 performed as a sheet or web on the wire of a paper-making machine, for example a Fourdrinier machine, and is treated to destroy the surface activity of the surface active agent. The treated material is then saturated with an organic water-repellent material and is thereafter heated, in any suitable known manner, to effect drying of the non-woven fibrous sheet or web. The non-woven fibrous sheet material can be treated to destroy the surface activity of surface active agent therein either by washing in a suitable chemical solution or by application of a suitable chemical solution with a size press, for example on the machine on which the non-woven fibrous sheet material is produced.

A surface active agent which can be used is sodium dodecyl benzene sulphonate (sold under the trade name NANSA SL30), and the surface activity of this cent aluminium sulphate solution. Other materials which can be used to destroy the surface activity are solutions of or mixes containing aluminium triformate, aluminium chloride and zirconium acetate.

The water-repellent material is preferably applied in admixture with a latex, in which case the saturated material is heated to a temperature sufficient to effect curing of the latex and the water-repellent material.

A suitable water-repellent material is an organic chromium derivative sold under the trade name QUIN- TOLAN W by Imperial Chemical Industries Limited (i.e. provided in an aqueous isopropanol solution) and this has been successfully used in admixture with an acrylic latex supplied by National Adhesives and Resins Ltd. under their reference 2873 (i.e., a vinyl acetate/acrylic copolymer).

Other suitable water-repellent materials are a zirconium wax sold under the trade name MYSTOLENE by Catomance Limited, an organic chromium derivative sold under the tradename QUILON by E. I. Du Pont de Nemours and Co. (i.e., a solution of a Wemer-type chromium complex such as a 30 percent solution of stearato chromic chloride in isopropanol), and a modified melamine resin sold under the trade name PI-IOBOTEX by CIBA GEIGY A.G.

This invention will now be described by way of example with reference to specific workings thereof.

A 60 g/m base paper of percent kraft pulp and 30 percent rayon produced by the foam method described in British Pat. specification No. 1,129,757 using sodium dodecyl benzene sulphonate (NANSA SL30) as the surface active agent, was treated by washing with a 3 percent aluminium sulphate solution in order to destroy the surface activity of sodium dodecyl benzene sulphonate remaining in the base paper.

The base paper was then divided into two sets of samples, Set A and Set B. The samples of Set A were saturated with a 2 l solids ratio admixture of an acrylic latex (National Adhesives and Resins Ltd; 2873) and an organic water-repellent material (QUINTOLAN W), and the samples of Set B were saturated with a 4 l solids ratio admixture of the same materials.

The latex/QUINTOLAN W admixtures were prepared as follows:

The latex was diluted with equal parts by weight of water using 40 parts of wet latex as delivered at 45 per cent solids (wt/wt) and 40 parts of water for the samples of Set A and parts of wet latex and 80 parts of water for Set B. A portion of QUINTOLAN W solution was prepared by adding 28 parts of QUINTOLAN W to 220 parts by weight of water whilst stirring rapidly, and then .adding 2.5 parts hexamine dissolved in parts by weight of water to the QUINTOLAN W solution, while stirring, to buffer the solution. The two latex mixtures were then individually blended with a portion of QUINTOLAN W solution, prepared as stated, to produce two admixtures for saturation of the samples of Set A and Set B respectively.

After saturation the samples of each set were dried and cured on a rotary drying cylinder, some at a temperature of 100C and others at a temperature of 130C.

The samples were then tested to determine the amount of latex and QUINTOLAN W picked up by the samples, measured as a percentage of the initial weight, i.e., 60 g/m of the base paper before saturation, and the samples were given a repellency test involving subjecting each sample to a l 10 mm head of l percent sodium chloride solution and determining the time taken for any of the water to penetrate the sample.

The results of these tests are given in the following table: MM.

5. A method of producing a water-repellent nonwoven fibrous sheet material comprising the steps of forming a suspension of fibres in a foam containing water, air and an anionic surface active agent; forming a non-woven fibrous sheet material from the suspension; washing the non-woven fibrous sheet material to destroy the surface activity of said surface active agent via chemical reaction with a solution containing a chemical selected from the group consisting of aluminum sulphate, aluminum triformate, aluminum chloride, and zirconium acetate; saturating the washed material with an organic water-repellent material; and heating the saturated material to effect drying thereof.

6. The method according to claim 5 in which saturation of the treated material is effected with said organic water-repellent material admixed with a latex and the saturated material is heated to a temperature sufficient to effect curing of the latex and water-repellent material.

7. The method according to claim 6 in which the t sat waer at.iswyrate yith a dmixt ts 99m.-

1 WATER REPELLENCY Set and Cure Number Average Average Average Average Range Temperature of Pickup Quintolan W Latex In Penetration Time (Mins) (C) Samples (wt%) in sample (wt7c) Sample (wt%) Time (Mins) l00 4 11.5 3.8 7.6 50.0 7.0 Set A 130 4 9.2 3.1 6.2 *100 100 4 9.5 1.9 7.6 37.l 5.0 Set B The test was terminated in all four cases We claim:

1. A method of producing a water-repellent nonwoven fibrous sheet material comprising the steps of forming a suspension of fibres in a foam containing water, air, and an anionic surface active agent; forming a nonwoven fibrous sheet material from the suspension; treating the non-woven fibrous sheet material to destroy the surface activity of said surface active agent in the material via chemical reaction with polyvalent metal cations; saturating the treated material with an organic water-repellent material; and heating the saturated material to effect drying thereof.

2. The method according to claim 1 in which said saturation of the treated material is effected with said organic water-repellent material admixed with a latex and the saturated material is heated to a temperature sufficient to effect curing of the latex and water: pellentmater alt T i 3. The method according to claim 2 in which said admixture comprises stearato chromic chloride in isopropanol and a vinyl acetate/acrylic copolymer latex.

4. The method according to claim 3 in which said admixture is prepared by diluting wet latex using equal parts by weight of said latex and water, preparing said organic water-repellent material by adding 28 parts by weight of said stearato chromic chloride in isopropanol to 220 partsby weight of water while stirring rapidly, adding 2.5 parts by weight of hexamine dissolved in IS parts by weight of water while stirring to buffer the solution, and blending the diluted latex with said organic water-repellent material.

prising stearato chromic chloride in isopropanol and a vinyl acetate/acrylic copolymer latex.

8. The method according to claim 7 in which said admixture is prepared by diluting wet latex using equal parts by weight of latex and water, preparing a waterrepellent material by adding 28 parts by weight of the stearato chromic chloride in isopropanol to 220 parts by weight of water while stirring rapidly, adding 2.5 parts by weight of hexamine dissolved in 15 parts by weight of water while stirring to buffer the solution, and blending the diluted latex with said water-repellent material.

9. A method of producing a water-repellent nonwoven fibrous sheet material comprising the steps of forming a suspension of fibres in a foam containing water, air, and a sodium dodecyl benzene sulphonate surface active agent; forming a non-woven fibrous sheet material from the suspension; washing the non-woven sheet material to destroy said surface active agent via chemical reaction with a 2 percent to 5 percent aluminium sulphate solution; saturating the treated material with an organic water-repellent material; and heating the saturated material to effect drying thereof.

10. The method according to claim 9 in which saturation of the treated material is effected with said organic water-repellent material admixed with a latex and the saturated material is heated to a temperature sufficient to effect curing of the latex and said water-repellent material.

11. The method according to claim 10 in which the treated material is saturated with an admixture comprising stearato chromic chloride in isopropanol and a vinyl acetate/acrylic copolymer latex.

12. The method according to claim 11 in which said admixture is prepared by diluting wet latex using equal parts by weight of latex and water, preparing a waterrepellent material by adding 28 parts by weight of the terial. 

1. A METHOD OF PRODUCING A WATER-REPELLENT NONWOVEN FIBROUS SHEET MATERIAL COMPRISING THE STEPS OF FORMING A SUSPENSION OF FIBRES IN A FOAM CONTAINING WATER, AIR, AND AN ANIONIC SURFACE ACTIVE AGENT, FORMING A NON-WOVEN FIBROUS SHEET MATERIAL FROM THE SUSPENSION, TREATING THE NON-WOVEN FIBROUS SHEET MATERIAL TO DESTROY THE SURFACE ACTIVITY OF SAID SURFACE ACTIVE AGENT IN THE MATERIAL VIA CHEMICAL REACTION WITH POLYVALENT METAL CATIONS, SATURATING THE TREATED MATERIAL WITH AN ORGANIC WATER-REPELLENT MATERIAL, AND HEATING THE SATURATED MATERIAL TO EFFECT DRYING THEREOF.
 2. The method according to claim 1 in which said saturation of the treated material is effected with said organic waterrepellent material admixed with a latex and the saturated material is heated to a temperature sufficient to effect curing of the latex and water-repellent material.
 3. The method according to claim 2 in which said admixture comprises stearato chromic chloride in isopropanol and a vinyl acetate/acrylic copolymer latex.
 4. The method according to claim 3 in which said admixture is prepared by diluting wet latex using equal parts by weight of said latex and water, preparing said organic water-repellent material by adding 28 parts by weight of said stearato chromic chloride in isopropanol to 220 parts by weight of water while stirring rapidly, adding 2.5 parts by weight of hexamine dissolved in 15 parts by weight of water while stirring to buffer the solution, and blending the diluted latex with said organic water-repellent material.
 5. A method of producing a water-repellent non-woven fibrous sheet material comprising the steps of forming a suspension of fibres in a foam containing water, air and an anionic surface active agent; forming a non-woven fibrous sheet material from the suspension; washing the non-woven fibrous sheet material to destroy the surface activity of said surface active agent via chemical reaction with a solution containing a chemical selected from the group consisting of aluminum sulphate, aluminum triformate, aluminum chloride, and zirconium acetate; saturating the washed material with an organic water-repellent material; and heating the saturated material to effect drying thereof.
 6. The method according to claim 5 in which saturation of the treated material is effected with said organic water-repellent material admixed with a Latex and the saturated material is heated to a temperature sufficient to effect curing of the latex and water-repellent material.
 7. The method according to claim 6 in which the treated material is saturated with an admixture comprising stearato chromic chloride in isopropanol and a vinyl acetate/acrylic copolymer latex.
 8. The method according to claim 7 in which said admixture is prepared by diluting wet latex using equal parts by weight of latex and water, preparing a water-repellent material by adding 28 parts by weight of the stearato chromic chloride in isopropanol to 220 parts by weight of water while stirring rapidly, adding 2.5 parts by weight of hexamine dissolved in 15 parts by weight of water while stirring to buffer the solution, and blending the diluted latex with said water-repellent material.
 9. A method of producing a water-repellent non-woven fibrous sheet material comprising the steps of forming a suspension of fibres in a foam containing water, air, and a sodium dodecyl benzene sulphonate surface active agent; forming a non-woven fibrous sheet material from the suspension; washing the non-woven sheet material to destroy said surface active agent via chemical reaction with a 2 percent to 5 percent aluminium sulphate solution; saturating the treated material with an organic water-repellent material; and heating the saturated material to effect drying thereof.
 10. The method according to claim 9 in which saturation of the treated material is effected with said organic water-repellent material admixed with a latex and the saturated material is heated to a temperature sufficient to effect curing of the latex and said water-repellent material.
 11. The method according to claim 10 in which the treated material is saturated with an admixture comprising stearato chromic chloride in isopropanol and a vinyl acetate/acrylic copolymer latex.
 12. The method according to claim 11 in which said admixture is prepared by diluting wet latex using equal parts by weight of latex and water, preparing a water-repellent material by adding 28 parts by weight of the stearato chromic chloride in isopropanol to 220 parts by weight of water while stirring rapidly, adding 2.5 parts by weight of hexamine dissolved in 15 parts by weight of water while stirring to buffer the solution, and blending the diluted latex with said water-repellent material. 